Abrasion resistant coating composition of an acrylic polymer, a polyester and a thermosetting constituent

ABSTRACT

A coating composition that forms a high quality abrasion resistant finish for fiberglass reinforced plastic sinks and bathtubs contains as the binder 1. AN ACRYLIC GRAFT COPOLYMER HAVING ATTACHED TO ITS BACKBONE SIDE CHAIN ESTER UNITS CONTAINING REACTIVE HYDROXYL GROUPS; II. a polyester of two or more dicarboxylic acids or anhydrides, a glycidyl ester, a glycol and a triol; III. an alkylolated medium formaldehyde resin; and contains pigments in a pigment to binder ratio of 50:100 to 250:100 of a blend of a primer pigment such as titanium dioxide and an abrasive pigment of zirconium silicate.

United States Patent Vasta June 27, 1972 [541 ABRASION RESISTANT COATINGCOMPOSITION OF AN ACRYLIC POLYMER, A POLYESTER AND A THERMOSETTINGCONSTITUENT 211 Appl. No.: 145,535

[52] vU.S. Cl. ..260/39 R, 260/850, 260/851,

260/862 [51] Int. Cl ..C08g 51/04 [58] Field of Search ..260/850, 851,862, 39

A [56] References Cited UNITED STATES PATENTS- 2,681,897 6/1954 Frazieret al ..260/45.2 3,366,706 1/1968 Vasta .....260/834 3,375,227 3/1968Hicks", .......260/47 3,376,271 4/1968 Masters et a1 ..260/78.4

3,600,459 8/1971 Vasta "260/834 3,622,651 11/1971 Vasta... ..260/8563,558,564 1/1971 Vasta .....260/77.5 3,382,294 5/1968 Christenson et al...260/873 X Primary ExaminerMorris Liebman Assistant Examiner-S. M.Person AttorneyHilmar L. Fricke [5 7] ABSTRACT A coating compositionthat forms a high quality abrasion resistant finish for fiberglassreinforced plastic sinks and bathtubs contains as the binder 1. anacrylic graft copolymer having attached to its backbone side chain esterunits containing reactive hydroxyl groups;

11. a polyester of two or more dicarboxylic acids or anhydrides, aglycidyl ester, a glycol and a triol;

111. an alkylolated medium formaldehyde resin; and contains pigments ina pigment to binder ratio of 50: 100 to 2501100 of a blend of a primerpigment such as titanium dioxide and an abrasive pigment of zirconiumsilicate.

11 Claims, No Drawings BACKGROUND or THE INVENTION This inventionrelates to a coating composition for reinforced plastic sheet materialsand in particular to a coating composition that forms a high qualityabrasion resistant finish on fiberglass reinforced plastic sinks vendingbathtubs. 30, 1968; al.,

Thermosetting coating compositions are well known in the art and havebeen widely used for autos, appliances, such as refrigerators, stoves,washers and dryers, air conditioners and the like and also for vendingmachines. Typical thermosetting coating compositions are shown inFrazier et al., US. Pat. No. 2,681,897, issued June 22, 1954; Vasta,U.S. Pat. No. 3,366,706, issued Jan. 30, 1968; Hicks, U.S. Pat. No.3,375,227, issued Mar. 26, 1968; Masters et al., U.S. Pat. No.3,376,271, issued Apr. 2, 1968; Vasta, US. Pat. No. 3,622,651 and Vasta,US. Pat. No. 3,600,459. However, these compositions do not provide thedegree of adhesion to a reinforced plastic substrate or the abrasionresistance required for finishes of bathtubs and sinks.

The novel coating composition of this invention forms a hard highlydurable abrasion resistant, stain resistant finish for sinks andbathtubs formed from reinforced plastic materials.

SUMMARY OF THE INVENTION The coating composition of this inventioncomprises -70 percent by weight of a film forming binder in an organicsolvent; wherein the filming forming binder consists essentially I 20-70percent by weight of a graft copolymer having a backbone of polymerizedmonomers which are either an aromatic hydrocarbon monomer havingvinylene groups, an alkyl acrylate, and alkyl methacrylate,acrylonitrile, methacrylonitrile and mixtures thereof wherein the alkylgroups have one to eight carbon atoms and has ester groups attacheddirectly to its backbone; these ester groups comprise about 10-75percent of the total weight of the polymer and consist essentially ofEster Group (A) and Ester Group (B), which is either or a mixture ofthese groups;

wherein the molar ratio of Ester Group (A) to Ester group (B) is fromabout 1:15 to 122.5; and wherein R is a saturated hydrocarbon radicalhaving two to 10 carbon atoms,

R is selected from the group consisting of alkylene,

in which R is defined above;

3. ethylene glycol, propylene glycol, 1,3-butane diol, 1,4-

butane diol or neopentyl glycol; and

4. trimethylol ethane, trimethylol propane, glycerine orpentaerythritol.

111. 15-55 percent by weight of a melamine/fonnaldehyde resin that hasat least been partially reacted with a monohydric alcohol having one tofour carbon atoms; and containing pigments in a pigment to binder ratioof 50: to 250:100, wherein the pigments comprise a primer pigment and anabrasive pigment in a weight ratio of primer pigment to abrasive pigmentof about 2:1 to about 1:5.

DESCRIPTION OF THE INVENTION Preferably, the novel coating compositionof this invention has a binder content of 40-60 percent by weight andthe binder comprises 40-50 percent by weight of the graft copolymer,20-30 percentby weight of the polyester and 20-40 percent by weight ofthe melamine/formaldehyde resin. Also, the preferred compositioncontains titanium dioxide as the primer pigment and zirconium silicateas the abrasive pigment.

The graft copolymer used in the novel process of this inven- .tionutilizes ethylenically unsaturated monomers for the backbone. Typicalmonomers that can be used for the backbone are, for example, aromatichydrocarbons having vinylene groups, such as styrene, alkyl substitutedstyrene, such as a-methyl styrene; vinyl toluene; acrylonitrilemethacrylonitrile; esters of methacrylic acid and acrylic acid,preferably acrylic esters having one to eight carbon atoms in the alkylgroup, such as methyl methacrylate, ethyl methacrylate, propylmethacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexylmethacrylate, and the like, methyl acrylate, ethyl acrylate, propylacrylate, butyl acrylate, hexyl acrylate, 2-ethylhexylacrylate and thelike or mixtures of these monomers. Small amounts of ethylenicallyunsaturated carboxylic acids can also be used in the backbone, such asacrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleicacid and the like.

Particularly useful monomers or combinations of monomers which form thebackbone of high quality polymers of this in-,

vention are, for example, styrene, methyl methacrylate, butylmethacrylate, ethyl acrylate, acrylonitrile and methacrylonitrile.

Ester Group (A) of the graft copolymer used in this invention isprovided by a hydroxyalkyl substituted vinyl addition monomer, such ashydroxyalkyl methacrylate, a hydroxyalkyl acrylate, a hydroxyalkylmaleate, hydroxyalkyl itaconate, or a mixture of these in which thealkyl group contains two to 10 carbon atoms. The hydroxyalkyl monomer ispolymerized with the aforementioned backbone monomers.

Preferred hydroxyalkyl monomers used for forming the graft copolymer ofthis invention are, for example, hydroxyethyl methacrylate,hydroxypropyl methacrylate, hydroxybutyl methacrylate, hydroxyoctylmethacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate,hydroxybutyl acrylate, hydroxyoctyl acrylate and the like. Preferred arehydroxyalkyl methacrylates or acrylates in which the alkyl groupscontain two to four carbon atoms.

Ester Group (B) is the esterification product of the aforementionedhydroxyalkyl monomers, an anhydride of a dicarboxylic acid and aglycidyl ester. This ester group is polymerized into the polymerbackbone through the ethylenic unsaturation of the aforementionedhydroxyalkyl monomers.

The anhydride used for forming Ester Group (B) has the formula wherein Ris either alkylene, vinylene, aromatic, carbocyclic or a heterocyclicradical. The anhydride reacts with the hydroxyalkyl monomer and alsoreacts with the glycidyl ester to form Group (B).

Anhydrides useful in this invention in which R is an alkylene group areformed from dicarboxylic acids of the general formula (CH, ),,(COOHwhere n is forom 2-l0. Typical dicarboxylic acids of this group areglutaric, adipic, pimelic, succinic acids and the like. The preferred isan anhydride of succinic acid.

Useful anhydrides in which R is a vinylene group are derived fromdicarboxylic acids of the general formula wherein n is from 4-10.Typical dicarboxylic acids of this group are maleic and itaconic acids.

Another group of useful anhydrides are derived from dibasic aromaticacids, such as phthalic acid, uvitic acid and cumidic acid. Often it isdesirable to use a halogen substituted anhydride of one of the abovearomatic dicarboxylic acids, such as tetrabromo phthalic anhydride.Halogen substituted anhydrides in which the halogen substitutent iseither chlorine, bromine or fluorine are particularly useful in formingfire retardant coating compositions.

Anhydrides in which R is a carbocyclic radical are useful, such ashexahydrophthalic anhydride, which has the following formula ortetrahydrophthalic anhydride which has the following formula Anhydridesin which R is a heterocyclic radical are also useful. One particularlyuseful compound has the general formula:

chlorine.

The glycidyl ester used for forming Ester Group (B) has the formulawhere R is a saturated aliphatic hydrocarbon group containing one-26carbon atoms, or R is an ethylenically unsaturated aliphatic hydrocarbonradical of 12-18 carbon atoms derived from a drying oil fatty acid.

was.

Preferred for use because of the quality of the graft copolymer obtainedare esters where R is a tertiary saturated aliphatic hydrocarbon groupof the structure where R is -Cl-l, and R and R are alkyl groups of oneto 12 carbon atoms.

One particularly preferred glycidyl ester of this group because itimparts acid and alkali resistance to the final product is a mixedglycidyl ester described in U.S. Pat. No. 3,275,583, issued Sept. 27,1966, and is manufactured and sold by the Shell Chemical Company asCardura" E ester. This glycidyl ester is of a synthetic tertiarycarboxylic acid and has the general formula where R" is a tertiaryaliphatic hydrocarbon group of eight through 10 carbon atoms.

When R of the graft copolymer is an ethylenically unsaturated aliphatichydrocarbon radical of l2-l8 carbon atoms, the glycidyl ester isobtained by esterifying the acid chloride of one of the well knowndrying oil fatty acids, such as oleic acid, linoleic acid, linolenicacid, oleostearic acid and ricinoleic acid with glycidol. These acidsare commonly found in tung oil, linseed oil, dehydrated castor oil andsoya oil.

The preferred method for forming the above unsaturated glycidyl estersis to react the sodium salt of the fatty acid with epichlorohydrin. Thereaction is as follows:

Quaternary ammonium R'C O OCHzCH C Hr where R is from one of theaforementioned drying oil fatty acids.

Preferablyflhe graft copolymer used in this invention has 30 to 60percent of its total weight contributed by Ester Group (A) and (B).Also, these groups are present in the graft copolymer at a molar ratioof Ester Group (A) to Ester Group (B) of about l:l.5 to about 122.5, andpreferably, in a ratio of about 1:2.

One method for preparing the graft copolymer used in this invention isto first form Ester Group (B) by reacting in about an equal molar ratiothe above hydroxyalkyl monomers, the anhydride and the glycidyl ester.This esterification product is then reacted with the backbone monomersand the hydroxyalkyl monomers, which form Ester Group (A), to form thenovel polymer of this invention.

As a typical example, a hydroxyalkyl acrylate, aromatic anhydride and aglycidyl ester are charged into a reaction vessel with a suitablesolvent, such as toluene, xylene, acetone or an aromatic solvent and themixture is heated to its reflux temperature, which is about to 200 C.,for about 30 minutes to 3 hours. The backbone constituents of the graftcopolymer, such as styrene/methyl methacrylate and a hydroxyalkylacrylate with a suitable polymerization catalyst, such as tertiary butylperoxide, are then slowly added over a 1-4 hour period. The reactionmixture is heated to its reflux temperature which is about 80to 200 C.for about 30 minutes to 5 hours, preferably 2-4 hours until a graftcopolymer is formed that has the desired molecular weight, which isdetermined by the relative viscosity as described below. Additionalsolvent may then be added to dilute the polymer solution.

If the reaction rates of the monomer components used to form the-graftcopolymer used in this invention are suitable, all of the monomers canbe charged into a reaction vessel with a suitable solvent andpolymerization catalyst and heated to the reflux temperature which isabout 80 to 200 C. for 60 minutes to 5 hours.

Another method of preparing the graft copolymer used in this inventionis to charge the anhydride, for example, phthalic anhydride, into areaction vessel with a suitable solvent and heat the mixture for about30 minutesto efiect solution of the anhydride. The other monomerconstituents with a suitable polymerization catalyst are then slowlyadded over a l-4 hour period into the reaction vessel while maintaininga reflux temperature which is about 80-200 C. After the aboveingredientshave been added, the reaction mixture is maintained at itsreflux temperature for an additional 30 minutes to about 5 hours.

Suitable solvents which are used to prepare the graft copolymer used inthis invention are toluene, xylene, butyl the like. To prepare the EsterGroup (B) esterification catalysts, such as quarternary bases or saltsas benzyltrimethylammonium hydroxide, benzyltn'methylammonium chloride,octadecyltrimethylammonium chloride, or an amine, such as triethylamine,can be used.

The graft copolymer preferably has a relative viscosity of 0.9 to 1.4.The relative viscosity is the value obtained by dividing the efflux timeof a solution of the polymer by the efflux time of the solvent used toform the above polymer solution. The efflux times are measured accordingto the procedure of ASTM-D-445-46-T, Method B, using as the polymersolution 0.25 grams of the polymer in 50 cubic centimeters of ethylenedichloride as the solvent. The efflux times are measured at 25 C. in astandard apparatus, sold under the designation of a modified Ostwaldviscometer.

The polymer solution resulting from the aforementioned process issuitable for direct use in the preparation of the novel coatingcompositions.

The polyester used in the novel coating composition of this inventionpreferably is the esterification product of:

1. about 4-15 percent, by equivalents, maleic anhydride and about 30-41percent, by equivalents, of one or more dicarboxylic acids selected fromfumaric, itaconic, orthophthalic and isophthalic acids;

2. about 9-25 percent, by equivalents, of the glycidyl ester component;

3. about 5-27 percent, by equivalents, of the glycol component; and

4. about 23-28 percent, by equivalents, of the triol component.

acids, to form the anhydride constituent constituent of the polyestercompositions of this invention. The inclusion of maleic anhydride in thepolyester compositions improves the solubility of the parent polyestercompositions in the solvents used in formulating coating compositions.

The glycidyl ester constituent of the polyester is identical to theglycidyl ester described previously.

Typically suitable glycols used to prepare the polyester includeethylene glycol, propylene glycol, 1,3-butane diol, 1,4-

butane diol, neopentyl glycol and their equivalents. The inclusion ofethylene glycol in the polyester composition is particularly preferredbecause of the increased stain resistance imparted to the finishedcoating composition.

Suitable triol components of the polyester include trimethylol ethane,trimethylol propane and glycerine. Pentaerythritol preferably is used incombination with a mole to mole blend 'of a glycol. Trimethylol propaneis preferably used in the polyester compositions because it improves thearomatic solubility of the resin without adversely affecting the qualityof the thermosetting coating compositions.

To formulate a high quality coating composition, the ratio of glycidylester to glycol in the polyester composition should be carefullycontrolled. Control of the glycidyl ester to glycol ratio also preventspremature gelation and aids in achieving the desired cure and hardnessof the finished coating composition.

Preferably the ratio of glycidyl ester to glycol, expressed in weightequivalents of ester to weight equivalents of glycol, is about 0.25/1.00-2.25/ 1.00. For example, in a polyester formulation having 25.6equivalents trimethylol propane, 7.4 equivalents maleic anhydride, and37.0 equivalents orthophthalic'anhydride, 16.7 equivalents of glycidylester and 13.3 equivalents of e.g. glycol, e.g., corresponding to aratio of 1.25/ l .00, are satisfactory amounts to achieve a resinformulation having the requisite properties. Likewise, a suitablepolyester formulation'results, for example, if 12.8 equivalents ofglycidyl ester and 17.2 equivalents of glycol, e.g., corresponding to aratio of approximately 0.75/1 .00 are used.

The thermosetting resin used in the novel coating composition of thisinvention is a melamine/formaldehyde resin that has been at leastpartially reacted with a monohydric alcohol having one to four carbonatoms. These resins are prepared by conventional techniques in which alower alkyl alcohol, such as methanol, butanol, isobutanol, propanol,isopropanol, ethanol and the like, is reacted with themelamine/formaldehyde resin to provide pendent alkoxy groups. Onepreferred resin is a melamine/formaldehyde resin having three to five ofthe CH OH groups reacted with methanol. Another thermosetting resin thatcan be used in this invention is hexamethoxymethylol melamine which issold under the trade name Cymel" 300 and 30!. Generally, an acidcatalyst is used to cure the novel coating composition of this inventionformulated with hexamethoxymethylol melamine. Typical strong acidcatalysts are sulfuric acid, sulfonic acid, p-toluene sulfonic acid,naphthalene sulfonic acid, hydrochloric acid, phosphoric acid, oxalicacid, citric acid and mixtures thereof.

To provide the novel coating composition with abrasion resistance and toimprove the adhesion to plastic fiberglass reinforced substrates, ablend of a primer pigment and an abrasive pigment is used. Typicalprimer pigments that can be used are titanium dioxide, zinc oxide,barytes and the like. Typical abrasive pigments are zirconium silicate,mill flake powdered glass, sand flour and the like. Preferred is a blendof titanium dioxide and zirconium silicate in a weight ratio of about1:2 which provides a coating composition with outstanding abrasionresistance and adhesion to the plastic reinforced substrate.

Small amounts of other conventional pigments, dyes and lakes can beadded such as carbon black, iron blue, burnt sienna, cadmium red,monastral blue, cobalt blue, phthalocyanine blue, irgazin yellow,molybdate orange, monastral green and the like.

Metallic flakes such as aluminum flake can also be added to the novelcomposition to provide glamour, alone or in combination with the metalflake. Preferably, about 5-20 percent by weight based on the weight ofthe binder of cellulose acetate butyrate having a viscosity of 1 secondor above is used in the novel composition with metallic flake pigments.

The pigments are introduced into the coating composition by firstforming a mill base by conventional sand-grinding or ball-millingtechniques, and then blending the mill base with the film-forming resinsas shown in the following examples. lf

cellulose acetate butyrate is used, the mill base is formed on a rollmill with cellulose acetate butyrate and then blended with the filmforming resins.

The resins are prepared in solution and then blended with a mill base toform the novel coating composition. Any of the aforementioned solventscan be used to prepare the novel coating composition or to dilute thecomposition to a desired application viscosity. The novel coatingcomposition is applied by any of the conventional application methodssuch as spraying, electrostatic spraying, dipping, brushing, rollercoating, flow coating and the like. The coating is then baked at about100-200" C. for about 5 minutes to 2 hours to form a film about 0.5-lmils thick. The resulting finish has excellent abrasion resistance,excellent adhesion to the substrate, food and drug stain resistance andultraviolet light resistance.

The novel coating compositions of this invention can be applied to avariety of substrates, for example, metal, wood, glass, and plastics. Inparticular, the novel coating composition forms excellent finishes onfiberglass reinforced plastic substrates. These substrates are formedinto bathtubs, sinks, shower stall floors and the like and arecoated'with 3-6 mils of the dried and coalesced novel coatingcomposition of this invention. One typical fiberglass reinforced plasticsubstrate has a matrix of a mixed ester of glycol phthalate and glycolmaleate cross linked with styrene.

Another aspect of this invention is a clear paper coating composition ofthe above graft copolymer and polyester but a urea/formaldehyde resin isused as the cross linking agent. The amounts of the constituents andsolvents are about the same as those used above. This composition isapplied over a paper substrate and baked for about 0.5-2 minutes atabout l25-l7 5 C. Films of about 0. l-l mil are applied. The resultingfinish is flexible, clear and glossy and is resistant to solvents.

The following examples illustrate the invention. All quantities are on aweight basis unless otherwise indicated.

EXAMPLE I A mill base is prepared as follows:

Parts By Weight Titanium Dioxide Pigment (Rutile) 200 Zirconium SilicatePigment 1 400 Acrylic Resin Solution (55% polymer solids in xylene andcellosolve acetate in which the polymer is 29.5% styrene, l5.0% methylmethacrylate, l6.5% hydroxyethyl acrylate, 14.0% phthalic anhydride and25.0% Cardura E" ester, prepared according to Example 1 of Vasta U.S.3,622,65l 200 Diacetone Alcohol 200 Total 1000 The above ingredients areblended together and charged into a conventional sand mill and ground to0.5 mil fineness.

A coating composition is prepared by blending the following ingredients:

Parts By Weight Mill base (prepared above) 250.0 Acrylic Resin Solution(described above) 40.0 Polyester Solution (60% polymer solids in xylenein which the polymer is of l89 parts of Cardura E ester", 49 partsethylene glycol, 107 parts trimethylol propane, 33 parts maleicanhydride and 225 parts of orthophthalic anhydride prepared according toExample l of U.S. 3,600,459 41.5 Uformite" MM83 Solution (80% solids inmethanol of a partially methylated melamine formaldehyde resin) 37.5Aromatic Naphtha Solvent Boiling Point 165C. 16.0

Total 385.0

[*Cardura" E ester (a mixed ester described in U.S.P. 3,275,583, issuedSeptember 27, 1966, and is a glycidyl ester of a synthetic tertiarycarboxylic acid of the formula where R is a tertiary aliphatichydrocarbon group of 8-10 carbon atoms)].

Total Solids 65% Pigment to Binder Ratio 150:100 Binder Acrylic Resin45% Polyester Resin 25% Uformite" Resin 30% Viscosity 4 sec. measured ina No. 10' Parlin Cup at 25C.

The above coating composition is diluted to a spray viscosity of 30 sec.measured in a No. 2 Zahn cup and a finish is then sprayed on to afiberglass reinforced plastic sheet. The fiberglass reinforced plasticsheet contains a resin matrix of glycol phthalate/glycol maleate estercross linked with polymerized styrene monomers and contains a fiberglassreinforcing filler, calcium carbonate and titanium dioxide pigments. Thesolvent is allowed to flash from the finish for about 15 minutes andthen the finish is baked for 45 minutes at The resulting finish is about3-5 mils thick.

The finish has excellent adhesion to the fiberglass reinforcedsubstrate, excellent abrasion resistance, good resistance to staining byfoods and drugs and excellent resistance to ultraviolet lightdegradation.

EXAMPLE 2 A coating composition is prepared by blending the followingingredients:

Parts By Weight Acrylic Resin Solution (described in Example 1) 45Polyester Solution (described in Example 1) 42 Urea/formaldehydeSolution (60% solids in butanol) 84 Total 171 The above ingredients arethoroughly blended together. The above composition is then diluted to a30 percent solids content by the addition of a solvent of a 50:50mixture of toluene/isopropanol. About 5 parts by weight of a 20 percentsolution of paratoluene sulfonic acid are then added and blended withthe composition.

The resulting composition is applied to a paper and baked for 30 secondsat C. to form a 0.2-0.5 mil thick coating. The coating is glossy,flexible and withstands 20-30 rubs with a cloth soaked with methyl ethylketone.

What is claimed is:

1. A coating composition comprising 10-70 percent by weight of a filmforming binder in an organic solvent; wherein the film forming binderconsists essentially of I. 20-70 percent by weight of a graft copolymerhaving a backbone of polymerized monomers selected from the groupconsisting of polymerized monomers of an aromatic hydrocarbon havingvinylene groups, an alkyl acrylate, an alkyl methacrylate,acrylonitrile, methacrylonitrile and mixtures thereof wherein the alkylgroups have one-8 carbon atoms and having ester groups attached directlyto its backbone, said ester groups comprising about 10 to 75 percent ofthe total weight of the polymer and consisting essentially of EsterGroup (A) and Ester Group (B) selected from the group consisting ofm-oJi-R or mixtures thereof, wherein the molar ratio of Ester Group (A)to Ester Group (B) is from about 121.5 to 1:25; and wherein R is asaturated hydrocarbon radical containingtwo-IO carbon atoms; R isselected from the group consisting of alkylene,

vinylene, aromatic, carbocylic and heteroradicals,'and R is selectedfrom the group consisting of a saturated aliphatic hydrocarbon radicalhaving one to 26 carbon atoms and an ethylenically unsaturated aliphatichydrocarbon radical having 12 to l8 carbon atoms;

II. 5-40 percent by weight of a polyester consisting essentially of (l)a mixture of maleic anhydride and at least one dicarboxylic acidselected from the group consisting of fumaric acid, itaconic acid,ortho-phthalic acid an isophthalic acid; (2) a glycidyl ester having theformula wherein R is defined above; (3) a glycol selected from the groupconsisting of ethylene glycol, propylene glycol, 1,3- butane diol,1,4-butane diol and neopentyl glycol; and (4) a trio] selected from thegroup consisting of trimethylol ethane, trimethylol propane, glycerineand pentaerythritol; and

III. l5-55 percent by weight of a melamine/formaldehyde resin that hasat least been partially reacted with a monohydric alcohol having one tofour carbon atoms; and containing pigments in a pigment to binder ratioof 502100 to 250:100 wherein the pigments comprise a primer pigment andan abrasive pigment in a weight ratio of primer pigment to abrasivepigment of about 2:1 to about 1:5.

2. The coating composition of claim 1 having a binder content of 40-60percent by weight and wherein the binder consists essentially of 40-50percent by weight of the graft copolymer, -30 percent by weight of thepolyester and 20-40 percent by weight of the melamine/formaldehyderesin.

3. The coating composition of claim 2 wherein the graft copolymer has abackbone consisting essentially of styrene and an acrylic ester selectedfrom the group consisting of an alkyl methacrylate, an alkyl acrylateand mixture thereof in which the alkyl group contains one to eightcarbon atoms; in which R is a saturated hydrocarbon group having two tofour carbon atoms,

R is an aromatic radical, and

R is a tertiary hydrocarbon group having eight through 10 carbon atoms.4. The coating composition of claim 3 wherein the polyester consistsessentially of 1. about 4-15 percent, by equivalents, maleic anhydrideand about 3041 percent, by equivalents, of a dicarboxylic acid selectedfrom the group consisting of fumaric acid, itaconic acid, ortho-phthalicacid and ispophthalic acid; 2. about 9-25 percent, by equivalents, of aglycidyl ester having the formula wherein R is a tertiary hydrocarbongroup having eight through 10 carbon atoms;

3. about 5-27 percent, by equivalents, of a glycol selected from thegroup consisting of ethylene glycol, propylene glycol, 1,3-butane diol,l,4-butane diol, and neopentyl glycol; and v 4. about 23-28 percent, byequivalents, of a trio] selected from the group consisting oftrimethylol ethane, trimethylol propane, glycerine and pentaerythritol.

5. The coating composition of claim 4 in which three-five of the CH Ol-lgroups of the melamine/formaldehyde resin have been reacted withmethanol.

6. The coating composition of claim 5 in which the primer pigment istitanium dioxide and the abrasive pigment is zirconium silicate.

7. The coating composition of claim 2 wherein I. the graft copolymer hasa backbone of styrene and methyl -methacrylate and R is ethylene, R isphenylene and R is a tertiary aliphatic hydrocarbon group having eightthrough 10 carbon atoms;

11. the polyester is the reaction product of maleic anhydride,orthophthalicanhydride, ethylene glycol, trimethylol propane and aglycidyl ester wherein R is defined as above;

III. a melamine/formaldehyde resin having three-five of the -CH Ol-lgroups reacted with methanol; and

pigments in a pigment to binder ratio of about 150: 100 wherein theprimer pigment is titanium dioxide and the abrasive pigment is zirconiumsilicate.

8. A sheet material of a fiberglass reinforced plastic substrate havingon at least one side about a 01-10 mil dried coalesced finish of thecoating composition of claim I.

9. The sheet material of claim 8 in which the plastic is a glycolphthalate, glycol maleate copolyester cross-linked with styrene.

10. A coating composition consisting essentially of 5-50 percent of afilm forming binder in an organic solvent; wherein the binder consistsessentially of I. 20-70 percent by weight of the graft copolymer ofclaim II. 5-40 percent by weight of the polyester of claim 1; and

Ill. 15-55 percent of urea/formaldehyde resin.

11. A paper substrate coated with about 0.1-1 mil of the I driedcoalesced composition of claim 10.

2. about 9-25 percent, by equivalents, of a glycidyl ester having theformula wherein R3 is a tertiary hydrocarbon group having eight through10 carbon atoms;
 2. The coating composition of claim 1 having a bindercontent of 40-60 percent by weight and wherein the binder consistsessentially of 40-50 percent by weight of the graft copolymer, 20-30percent by weight of the polyester and 20-40 percent by weight of themelamine/formaldehyde resin.
 3. The coating composition of claim 2wherein the graft copolymer has a backbone consisting essentially ofstyrene and an acrylic ester selected from the group consisting of analkyl methacrylate, an alkyl acrylate and mixture thereof in which theaLkyl group contains one to eight carbon atoms; in which R1 is asaturated hydrocarbon group having two to four carbon atoms, R2 is anaromatic radical, and R3 is a tertiary hydrocarbon group having eightthrough 10 carbon atoms.
 3. about 5-27 percent, by equivalents, of aglycol selected from the group consisting of ethylene glycol, propyleneglycol, 1,3-butane diol, 1,4-butane diol, and neopentyl glycol; and 4.about 23-28 percent, by equivalents, of a triol selected from the groupconsisting of trimethylol ethane, trimethylol propane, glycerine andpentaerythritol.
 4. The coating composition of claim 3 wherein thepolyester consists essentially of
 5. The coating composition of claim 4in which three-five of the -CH2OH groups of the melamine/formaldehyderesin have been reacted with methanol.
 6. The coating composition ofclaim 5 in which the primer pigment is titanium dioxide and the abrasivepigment is zirconium silicate.
 7. The coating composition of claim 2wherein I. the graft copolymer has a backbone of styrene and methylmethacrylate and R1 is ethylene, R2 is phenylene and R3 is a tertiaryaliphatic hydrocarbon group having eight through 10 carbon atoms; II.the polyester is the reaction product of maleic anhydride, orthophthalicanhydride, ethylene glycol, trimethylol propane and a glycidyl esterwherein R3 is defined as above; III. a melamine/formaldehyde resinhaving three-five of the -CH2OH groups reacted with methanol; andpigments in a pigment to binder ratio of about 150:100 wherein theprimer pigment is titanium dioxide and the abrasive pigment is zirconiumsilicate.
 8. A sheet material of a fiberglass reinforced plasticsubstrate having on at least one side about a 0.1-10 mil dried coalescedfinish of the coating composition of claim
 1. 9. The sheet material ofclaim 8 in which the plastic is a glycol phthalate, glycol maleatecopolyester cross-linked with styrene.
 10. A coating compositionconsisting essentially of 5-50 percent of a film forming binder in anorganic solvent; wherein the binder consists essentially of I. 20-70percent by weight of the graft copolymer of claim 1; II. 5-40 percent byweight of the polyester of claim 1; and III. 15-55 percent ofurea/formaldehyde resin.
 11. A paper substrate coated with about 0.1-1mil of the dried coalesced composition of claim 10.